Add comment to linesplitter.bind.

sdk/lib/convert/line_splitter.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 part of dart.convert;
 
 // Character constants.
 const int _LF = 10;
 const int _CR = 13;
 
@@ skipping 40 matching lines @@
 
   List<String> convert(String data) => split(data).toList();
 
   StringConversionSink startChunkedConversion(Sink<String> sink) {
     if (sink is! StringConversionSink) {
       sink = new StringConversionSink.from(sink);
     }
     return new _LineSplitterSink(sink);
   }
 
+  // Override the base-class' bind, to provide a better type.
   Stream<String> bind(Stream<String> stream) => super.bind(stream);
 }
 
 // TODO(floitsch): deal with utf8.
 class _LineSplitterSink extends StringConversionSinkBase {
   final StringConversionSink _sink;
 
   /// The carry-over from the previous chunk.
   ///
   /// If the previous slice ended in a line without a line terminator,
@@ skipping 58 matching lines @@
       _sink.add(lines.substring(sliceStart, i));
       sliceStart = i + 1;
     }
     if (sliceStart < end) {
       _carry = lines.substring(sliceStart, end);
     } else {
       _skipLeadingLF = (char == _CR);
     }
   }
 }